1. Field of the Invention
The present invention relates to a semiconductor device having a package structure, and more particularly, relates to a semiconductor device having a WCSP type structure.
2. Description of the Background Art
The high integration of a semiconductor device mounted in an electronic device and the high frequency of a transmission signal have been expected increasingly in recent years. A CSP (Chip Size Package) serving as a semiconductor, which is packaged in an outline size substantially same as that of a semiconductor chip, has been proposed to cope with this expectation.
In recent years, with a view of decreasing a manufacturing cost or the like, a technical development of a WCSP (Waferlevel Chip Size Package) has been promoted. The WCSP comprises a CSP, in which its external terminal formation process is completed in a waferlevel and is individualized by dicing.
In this WCSP, there is known, as one example thereof, one having a structure such that an electrode pad and an external terminal, which are mounted on a semiconductor chip, are electrically connected via a wiring layer (a rewiring layer) for rearranging this external terminal in a desired position.
In the WCSP having the above described rewiring layer, a degree of freedom in a wire design may be improved due to the rewiring layer.
In the case of transmitting a high frequency signal by the use of the above described WCSP having the rewiring layer, it is desirable that, between a circuit element, which is provided to a semiconductor chip, and a signal line, namely, a rewiring layer to be electrically connected to the foregoing circuit element via an electrode pad, impedance of the both is matched.
By avoiding mismatch between the circuit element and the signal line, attenuation of the transmission signal arising from the reflection or the like of the transmission signal generated in the vicinity of a joint between the electrode pad and the signal line can be restrained.
However, regardless of that a characteristic impedance of the signal line in the WCSP is sufficiently larger than the impedance of the circuit element, and an effective method has not been proposed to match the impedance between both by decreasing the characteristic impedance of the signal line.